Track and footpath conditions were investigated on the Aberffraw sand dunes, Anglesey. Soil bulk density and penetration resistance were related to the number of passages by cars or walkers and was increased on tracks and footpaths; compaction was examined to 50 cm depth. Trampling increased soil moisture in dry areas and compaction per se as probably beneficial to plants. Vegetation was shown by multivariate analysis to be related to the soil parameters. Light trampling favoured dicotyledonous species but they were later eliminated and monooctiledonous species survived with a reduction in biomass and species number. Track OccAxee.c*es. prefers-n-0-e indices were calculated for the common species and survival strategies considered; tillering capacity may be more important than protected meristems. Trampling and wear by vehicles was applied to undamaged vegetation and the effect measured before and after recovery. Intensity was found to be more important than the effect of frequency. 1820 walkers or 20Q vehicles reduced cover to 50,'; in the summer; vehicles were more destructive in winter. Physical carrying capacity was calculated and relative vulnerability of various habitats was estimated from data of other workers. Soils were found to decompress when traffic was removed but vegetation initially inhibited the process. Tillage, seeding and the effects of fertiliser on vegetation regeneration were studied; the first inhibiting and the latter two treatments accelerating the process. Turves in greenhol.se conditions were used to predict the results. The desirable end point was considered from the management point of view. The effect of a track on the microclimate was studied with emphasis on thermal Characteristics: vegetation removal had a greater effect than soil compaction. The effect on plants in relation to their distribution and morphology was discussed. Models describing the ecological changes caused by trampling and the physical carrying capacity of sand dune pasture were constructed.